REPUBLIKA.CO.ID, MEXICO CITY -- Rescuers labored against long odds into the dawn on Thursday to save a 12-year-old schoolgirl and untold other survivors who may be trapped beneath crumpled buildings in central Mexico following the country's deadliest earthquake in 32 years.

More than 50 survivors have been plucked from several disaster sites since Tuesday afternoon's 7.1-magnitude quake, leading to impassioned choruses of "Yes we can!" from the first responders, volunteers and spectators gathered around the ruins.

At least 237 others have died and 1,900 were injured.

As the odds of survival lengthened with each passing hour, officials vowed to continue with search-and-rescue efforts such as the one at a collapsed school in southern Mexico City where Navy-led rescuers could communicate with the 12-year-old girl but were still unable to dig her free.

Eleven other children were rescued from the Enrique Rebsamen School, where the students are aged roughly six to 15 but 21 students and four adults there were killed.

Rescuers previously had seen a hand protruding from the debris and the girl wiggled her fingers when asked if she was still alive, according to broadcaster Televisa, whose cameras and reporters had special access to the scene to provide nonstop live coverage.

But some 15 hours into the effort, Admiral Jose Luis Vergara said rescuers still could not pinpoint her location.

"There's a girl alive in there, we're pretty sure of that, but we still don't know how to get to her," Vergara told Televisa.

"The hours that have passed complicate the chances of finding alive or in good health the person who might be trapped," he said.

As with other disaster sites throughout central Mexico, officials dared not employ heavy lifting equipment for fear of crushing anyone below.

Throughout the capital, crews were joined by volunteers and bystanders who used dogs, cameras, motion detectors and heat-seeking equipment to detect victims who may still be alive. Some 52 buildings collapsed in Mexico City alone and more in the surrounding states.